1. Field
One or more embodiments relate to an electrode for a lithium secondary battery, a method of manufacturing the same, and a lithium secondary battery including the electrode.
2. Description of the Related Technology
A lithium secondary battery consists of a positive electrode, a negative electrode, a separator, and an electrolyte. During charging, lithium ions are deintercalated from the positive electrode and migrate toward the negative electrode, and during discharging, lithium ions are deintercalated from the negative electrode and return to the positive electrode. The positive and negative electrodes and the electrolyte do not induce any chemical reactions.
Typically, an electrode includes a mixture including an active material for storing energy, a conducting agent for supplying electric conductivity, and a binder. In general, as an active material for the positive electrode, a lithium transition metal oxide is used, and as an active material for the negative electrode, a carbonaceous active material is used. To manufacture the electrode, the mixture is mixed with a solvent to prepare a slurry, and then the slurry is coated and dried on a current collector. In this case, the binder improves dispersion of the conducting agent, an adhesive force between active material particles, between the active material and the current collector, and between the active material and the conducting agent, and conductivity of the conducting agent.
As the binder, a fluorine-based polymer material that is insoluble with respect to an organic electrolytic solution and is chemically stable, such as polyvinylidene fluoride (PVdF), is widely used.
However, if the fluorine-based polymer material, such as PVdF, is used as the binder, since chains of the fluorine-based polymer material are entangled, the binder has a high swelling ratio that indicates a degree to which the binder swells when the electrolytic solution permeates thereinto. Also, due to the interaction between the chains, when a nano-sized active material and the conducting agent are used, the solvent may separately leak out. Also, the swollen binder leads to an increase in a distance between active material particles, thereby increasing resistance of an electrode including the binder.